The semiconductor industry continues to strive for continuous device miniaturization that is driven by the need for mobile, and high-performance systems in emerging industries such as autonomous vehicles, virtual reality, and future mobile devices. To accomplish this feat, new, high-performance materials are needed to circumvent inherent engineering and physics issues encountered in rapid reduction of features in microelectronic devices.
Iridium is a new proposed material for integration owing to its high melting point (ability to withstand high current densities), exceptional density, and ability to conduct electrical current. Iridium and iridium based thin films have attractive material and conductive properties. Iridium films have been proposed for applications from front end to back end parts of semiconductor and microelectronic devices.
Thin-films of iridium would ideally be deposited using thin-film deposition techniques such as Chemical Vapor Deposition (CVD) and Atomic Layer Deposition (ALD) owing to their inherent ability to deposit material in a high-throughput, conformal, and precise fashion.
Chemical vapor deposition (CVD) is one of the most common deposition processes employed for depositing layers on a substrate. CVD is a flux-dependent deposition technique that uses precise control of the substrate temperature and the precursors introduced into the processing chamber in order to produce a desired layer of uniform thickness. The reaction parameters become more critical as substrate size increases, creating a need for more complexity in chamber design and gas flow technique to maintain adequate uniformity.
A variant of CVD that demonstrates excellent step coverage is cyclical deposition or atomic layer deposition (ALD). Cyclical deposition is based upon atomic layer epitaxy (ALE) and employs chemisorption techniques to deliver precursor molecules on a substrate surface in sequential cycles. The cycle exposes the substrate surface to a first precursor, a purge gas, a second precursor and the purge gas. The first and second precursors react to form a product compound as a film on the substrate surface. The cycle is repeated to form the layer to a desired thickness.
Processing an iridium precursor often involves using oxygen or an oxidizing co-reagent. Use of oxygen and oxidizing co-reagents can be incompatible with other adjacent films in the device stack. Therefore, there is a need in the art for iridium precursors and co-reagents that react to form iridium metal and iridium based thin films without an oxidizing co-reagent.
The advancing complexity of advanced microelectronic devices is placing stringent demands on currently used deposition techniques. Unfortunately, there is a limited number of viable chemical precursors available that have the requisite properties of robust thermal stability, high reactivity, and vapor pressure suitable for film growth to occur.
In addition, precursors that often meet these properties still suffer from poor long-term stability and lead to thin films that contain elevated concentrations of contaminants such as oxygen, nitrogen, and/or halides that are often deleterious to the target film application. Therefore, there is a need for improved thin film precursors for iridium.